Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


PCB Component Legend Under SMT Pad/Land

dreamsniper

#9642

PCB Component Legend Under SMT Pad/Land | 13 September, 1999

I noticed that some of our pcb's component legend/designation are unreadable as they are placed under smt pads. Is this correct and according to standard? Although we don't have any problems with them as of now, I would like to know the effects on the process of this type of PCB Design so i could feedback to our Design Engineer. The pcb size is too small and too dense that there's no more space for the component legend. Is it better to eliminate the legend if this is the case ? thanks and regards, dreamsniper

reply »

Earl Moon

#9643

Re: PCB Component Legend Under SMT Pad/Land | 13 September, 1999

| I noticed that some of our pcb's component legend/designation are unreadable as they are placed under smt pads. Is this correct and according to standard? Although we don't have any problems with them as of now, I would like to know the effects on the process of this type of PCB Design so i could feedback to our Design Engineer. The pcb size is too small and too dense that there's no more space for the component legend. | Is it better to eliminate the legend if this is the case ? | thanks and regards, | dreamsniper | | As you know, If you can't read it, it's of no value during inspection and test. Also, if under small device types it provides potential for ink on pads to prevent solderabillity.

Also, can't you rewire the keyboard on the GSM as a temporary fix at least?

Earl Moon

reply »

Brian

#9644

Re: PCB Component Legend Under SMT Pad/Land | 13 September, 1999

| I noticed that some of our pcb's component legend/designation are unreadable as they are placed under smt pads. Is this correct and according to standard? Although we don't have any problems with them as of now, I would like to know the effects on the process of this type of PCB Design so i could feedback to our Design Engineer. The pcb size is too small and too dense that there's no more space for the component legend. | Is it better to eliminate the legend if this is the case ? | thanks and regards, | dreamsniper

What Earl says is right, but I'm not reading you right. Surely you mean under the SM device? It is physically impossible to have the legend UNDER the pads with normal manufacturing practice - and damned difficult with VERY abnormal. As Earl says, if you have legends on the pads, you are in BIG trouble with soldering.

I'll add one rider to Earl's remarks: if the legend is hidden by the components, then it may still be useful during assembly preparation and when replacing faulty components, although there sure ain't much space under most passive devices, any more than legible values/colour codes on them are a thing of the past!

Brian | |

reply »

#9645

Re: PCB Component Legend Under SMT Pad/Land | 13 September, 1999

| | I noticed that some of our pcb's component legend/designation are unreadable as they are placed under smt pads. Is this correct and according to standard? Although we don't have any problems with them as of now, I would like to know the effects on the process of this type of PCB Design so i could feedback to our Design Engineer. The pcb size is too small and too dense that there's no more space for the component legend. | | Is it better to eliminate the legend if this is the case ? | | thanks and regards, | | dreamsniper | | What Earl says is right, but I'm not reading you right. Surely you mean under the SM device? It is physically impossible to have the legend UNDER the pads with normal manufacturing practice - and damned difficult with VERY abnormal. As Earl says, if you have legends on the pads, you are in BIG trouble with soldering. | | I'll add one rider to Earl's remarks: if the legend is hidden by the components, then it may still be useful during assembly preparation and when replacing faulty components, although there sure ain't much space under most passive devices, any more than legible values/colour codes on them are a thing of the past! | | Brian | | | |another problem would be the thickness of the legend ink lifting the stencil slightly and preventing complete gasketing. this is especially true for component outline features and fine pitch components. John Thorup |

reply »

Reflow Ovens thermal process improvement

PCB X-Ray Inspection